1. Field of the Invention
A present invention relates to a light transmitting apparatus having a bending part, which is used in transmitting, natural light artificial light or the like.
2. Description of the Conventional Art
A light transmitting device has been known in which the light is transmitted inside cylindrical duct so that the light is reflected in the inside of the duct. In a light transmitting apparatus, a straight and cylindrical duct is used to transmit the light linearly. However, a bending part is necessary to transmit the light to a predetermined place.
For example, the conventional light transmitting apparatus has cylindrical ducts. 1, 1' and a bending part 10 as shown in FIG. 2A. The cross section of the bending part is shown in FIG. 2D. As shown in FIGS. 2B and 2C, the conventional light transmitting has a duct 1, 1'. The bending part 10 includes a flat reflecting mirror 2 inclined at 45.degree. to obtain a regular reflection effect with respect to the light transmission direction, triangular side reflecting mirrors 3 mounted at both sides of the flat reflecting mirror 2 so as to transmit the light in the perpendicular direction, and coupling members 5, 5' which are respectively connected with the ducts 1, 1' so as to connect the bending part 10 with the ducts 1, 1'. Consequently, the light transmitted in the duct 1 can be introduced into the duct 1' which is perpendicular to the duct 1.
However, the shape of a light distribution of an outgoing light which is transmitted in the duct 1 having the reflection effect depends on the shape of a light distribution of a incoming light, but generally, is axially symmetrical along the light transmission direction. Some part of the axially symmetrical light which is reflected by the center portion of the flat reflecting mirror 2 being set at an angle so as to perform a regular reflection is effectively reflected to a desirable direction as a primary reflected light. However, since the number of reflections of the light reflected by the side flat reflecting mirrors 3 is two or more, the light reflected by the side flat reflecting mirrors 3 cannot be reflected effectively. Such a problem has been an obstruction in light transmission.
In addition, for example, the other conventional light transmitting apparatus has the duct 1, 1' and a bending part 6 having a circular cross section as shown in FIGS. 3A and 3B. The transmitting efficiency of this light transmitting apparatus is better than the former conventional light transmitting apparatus. However, this light transmitting device also has a problem in the transmitting efficiency.